<!DOCTYPE html>
<html lang="zh-cn">
<head>
	<meta charset="UTF-8">
	<title>绘制球形</title>
</head>
<body>
	 <canvas id="c1" width="600" height="400" style="border: solid 1px gray; margin: 10px auto;display: block;"></canvas>
</body>
<script type="text/javascript">
	window.onload = function () {
		var c1 = document.getElementById('c1');
		var ctx = c1.getContext('2d');
		ctx.lineWidth = 3;
		ctx.strokeStyle = '#00f';
		ctx.arc(200,200,100,0,0.5*Math.PI,true);
		ctx.stroke();
	}
</script>
</html>